The present invention pertains to sterilization indicators, more particularly, to indicator compositions that change color when exposed to ethylene oxide sterilization conditions.
Instruments and materials used in modern medical facilities such as hospitals, medical laboratories and other health service facilities, often require sterilization. Sterilization can be achieved by variety of technologies, such as steam sterilization, ethylene oxide gas sterilization, formaldehyde gas sterilization, plasma sterilization and ozone sterilization processes. Although steam sterilization is effective, it is not always appropriate, for example, for heat-sensitive materials such as biological materials, fiber optics, electronics, and many plastics.
Ethylene oxide sterilization is a common alternative to steam sterilization for such heat-sensitive objects and materials. Ethylene oxide gas used in ethylene oxide sterilization processes is a widely used alkylating agent, which can be used alone or in an admixture with an inert gaseous diluent such as carbon dioxide, nitrogen, trichloromonofluoromethane, dichlorodifluoromethane, and the like. Ethylene oxide gas can be used as a sporicidal and virucidal agent. Consequently, ethylene oxide sterilization is often employed to ensure total eradication of microorganisms.
Since ethylene oxide gas can readily diffuse through commonly employed packaging materials and is highly effective in killing microorganisms at temperature well below those required for heat or steam sterilization techniques, it enables efficient sterilization of many items, particularly those made of thermoplastic materials, which can be damaged under heat or steam sterilization conditions. Ethylene oxide sterilization generally involves placing an item in a chamber and subjecting it to ethylene oxide vapor. When used properly, ethylene oxide is not only lethal to all known microorganisms at ordinary temperature, but it is also non-corrosive, readily removed by aeration, easily handed and stored, and has a low toxicity to humans.
Various indicators for indicating that an article has undergone ethylene oxide sterilization are commercially available. For example, water-based ethylene oxide sterilization indicator inks and methods are disclosed in U.S. Pat. No. 6,800,124 and U.S. Pat. No. 7,141,214, which are assigned to the assignee of the present application, and incorporated herein by reference in their entirety.
The present invention provides improved methods and indicator compositions for indicating successful sterilization of articles by ethylene oxide sterilization.